As is commonly known, liquid fuel stored in a fuel reservoir emits fuel vapors when the liquid fuel is converted to a gas, typically during evaporation. An evaporative emission system is commonly used to reduce or recycle the fuel vapors that are vented from a fuel tank that supplies liquid fuel to a vehicle engine.
In addition, certain states, including California, require evaporative controls for some engines, such as small off-road engines (SORE). Fuel vapors generated in a fuel tank (and/or carburetor) can be forced by expansion to exit the fuel tank. Traditionally, these vapors have been routed through a length of tubing to a carbon canister, which is a structure that contains a fuel vapor absorbing material (e.g., charcoal) where the vapors can be trapped and/or absorbed. When the engine is subsequently operated the carbon canister is flushed with air to remove the absorbed fuel vapors from the carbon canister and the vapors are then pulled into the engine intake system to be burned.
Although the carbon canister can effectively absorb and release vapors they have numerous drawbacks. In particular, carbon canisters can be costly to purchase and maintain on a vehicle, and they can be difficult to mount on a vehicle in an efficient and aesthetic manner.
In addition, most vehicles utilize a roll-over valve to prevent the inadvertent flow of fuel from a fuel tank, such as through the carbon canister, when the vehicle is overturned. This configuration adds an additional component that must then be separately mounted to the vehicle along with additional tubing and fittings.
Accordingly, it would be desirable to provide an evaporative emission system that overcomes at least some of the aforementioned shortcomings.